Fish proteins with which fish flesh is enriched have extraordinarily high nutritive value. The fish proteins contain a large amount of nutrients necessary for human body, which are conducive to reducing contents of blood lipids and cholesterol, especially a large amount of DHA, which are able to promote development of a brain, and is an indispensable nutrient for growth of a nervous system. Therefore, more and more people choose to process and eat fish products. However, fishiness of fish products themselves has a huge influence on taste of processed food, and also molecular weights of proteins in the fish flesh are too large to be absorbed by human body. In some processing techniques of prior art, a common approach is to hydrolyze proteins with a large molecular weight in extreme pH and temperature condition, but this will adversely affect properties of the proteins.
More importantly, fish allergy is considered to be one of the most common food allergies since fish proteins contain a large number of allergens, such as parvalbumin, which is proved by IgE antibody to be able to cause more than 95% of people to develop allergy. Heating and chemical treatment are common methods for eliminating allergenicity, but the heating, which denatures the proteins, is unlikely to remove all allergens among the fish proteins, and the chemical treatment, which is mainly to reduce activity of trypsin inhibitors by chemical reagents, will inevitably give rise to food safety issues such as chemical residuals.
The patent publication No. CN102008004A discloses a method for preparation of fish protein powder enriched with fish skin proteins. This method mainly adopts a neutral protease and bromelain to conduct two-step enzymolysis of a fish skin material. Although the enzymolysis can reduce an average molecular weight of final products to below 6000 Da, the method fails to process and detect allergens in the final products, and thus it is not possible to determine whether the method can reduce allergenic activity, and additionally, the method has complicated operation steps.
Li Yang, et al., suggests a method for preparation of fish protein oligopeptide: proteins of mandarinfish flesh is hydrolyzed in a phosphate buffer with a pH value of 8.00 at 40° C. for 4 h using 2940 U/g of papain, reducing the antigenicity of final product of mandarinfish proteins by 58.33%. However, this method again fails to conduct study on allergenicity of parvalbumin, and besides, brings a concern that the enzymolysis product is highly likely to acquire new allergenicity due to exposure of a linear epitope which is originally hidden within a three dimensional protein structure or a hydrophobic region.